1. Field of the Invention
This invention relates generally to sensors utilizing elastomeric injection molded dome-caps such as are used in the prior art as simple momentary-On electrical switches. The present invention is specifically directed toward new uses of elastomeric injection molded dome-cap sensors, specifically using such devices in a novel manner as analog sensors.
2. Description of the Related Prior Art
Elastomeric injection molded dome-cap momentary-On switches (sensors) are well known and widely used in the prior art as switches incorporated in such common host devices as remote controls for televisions and stereos, and in electronic game control devices such as game pads for Nintendo, Sony and Sega game consoles, and some computer keyboards, etc. In all of the above mentioned host devices and in all known prior art where the elastomeric dome-cap sensor is employed, the injection molded dome-cap is always used as a component of a sensor having a single threshold serving as a simple make or break (closed or open) electrical switch in a circuit.
The term elastomeric is used to describe any rubber-like material, whether natural or synthetic.
Structurally, the prior art elastomeric injection molded dome-cap carries a normally raised conductive element or disk referred to as a pill or a carbon pill. The conductive pill is herein sometimes referred to as the "active element". The active element in prior art elastomeric injection molded dome-cap sensors is believed to be made of a binder of elastomeric or rubbery material binding carbon or carbon containing material and possibly other materials. The active element is located at the top inside of the non-conductive elastomeric dome-cap and above two proximal highly conductive elements or traces so that with depression of the dome-cap, such as with pressure applied by a finger, the active element is moved with the collapsing dome-cap into contact with both proximal conductive elements and closes an otherwise normally open circuit. Since the injection molded dome-cap is resilient, with release of pressure on the dome-cap it returns to a raised position carrying the active element with it to open the circuit. Electronic circuitry associated with the two proximal conductive elements, which are either bridged or not bridged by the active element of the elastomeric dome-cap, is circuitry which in the prior art has always been structured only to detect or read a threshold event, i.e., an open or closed (binary) state across the proximal conductive elements.
As those skilled in the art appreciate, most, but not all elastomeric injection molded dome-caps when depressed produce a soft snap which is a user discernable tactile feedback. This tactile feedback occurs when the dome-cap is depressed beyond a given point; the point being where a mechanical threshold is crossed and the tactile snap is produced. The snap defining the tactile sensation occurs just prior to the active element being brought into contact with the two proximal conductive elements. The tactile sensation is perceived by the user as occurring at the same time the sensor is activated, which in the prior art is when the switch is closed. The switch remains closed until such time as the user releases pressure on the dome-cap, at which time the dome-cap being made of elastomeric material returns to a raised position carrying the active element with it and off of the proximal conductive elements. The elastomeric injection molded dome-cap typically again produces a tactile sensation as it moves upward crossing the mechanical snap-through threshold. Elastomeric injection molded dome-caps are typically molded or are made primarily of thermoset rubber, are one-piece absent joints or seams, and provide excellent durability for a very low cost. The active element in the prior art is typically adhered to the inside top of the dome-cap during the injection molding phase of manufacturing the dome-cap.
Another type of prior art sensor is described in U.S. Pat. No. 3,806,471 issued Apr. 23, 1974 to R. J. Mitchell for "PRESSURE RESPONSIVE RESISTIVE MATERIAL". Mitchell describes sensors which utilize pressure-sensitive variable-conductance material to produce analog outputs. Mitchell does not use or suggest an elastomeric injection molded dome-cap used to either carry variable-conductance material or to transfer finger applied pressure into variable-conductance material. Mitchell also fails to recognize any need for or suggest the use of an elastomeric injection molded dome-cap to provide tactile feedback to the user upon actuation or de-actuation of the pressure-sensitive variable-conductance sensor. U.S. Pat. No. 4,315,238 issued Feb. 9, 1982 to F. Eventoff describes a pressure-sensitive bounceless switch absent a suggestion of using an elastomeric injection molded one-piece dome-cap or providing tactile feedback, and is thus considered to be cumulative prior art to the Mitchell disclosure.
There have been hundreds of millions of momentary-On elastomeric dome-cap style switches made and sold in the last 20 years. Pressure-sensitive variable-conductance sensors have also been known for decades and have always been quite expensive compared to elastomeric injection molded dome-cap switches. The prior art does not suggest the use of an inexpensive elastomeric injection molded dome-cap containing any pressure-sensitive variable-conductance material in association with circuitry structured for control or manipulation by the elastomeric dome-cap sensor applied as an analog sensor, or as a pressure-sensitive variable-conductance sensor which includes tactile feedback in association with circuitry structured for control or manipulation by the elastomeric dome-cap sensor applied as an analog sensor. Clearly an inexpensive injection molded elastomeric dome-cap pressure-sensitive variable-conductance sensor would be useful and of benefit, as also would be such a sensor having tactile feedback. Such sensors would be useful in a wide variety of applications wherein human input is required. Such applications include home electronics, computers and generally, but not limited to, devices operated by the human hand/finger inputs.
I have discovered, as will be detailed below, that a typical elastomeric injection molded dome-cap type switch when used as part of a novel structural combination or in a novel method fills a long standing need for a very inexpensive and durable pressure-sensitive variable-conductance sensor, and further one which can, if desired, supply tactile feedback.